Pneumatic tire casing for motor vehicles



May 13, 19240 E. HOPKINSON PNEUMATIC TIRE CASING FOR MOTOR VEHICLES 6Sheets-Sheet 1 Original Filed Jan. 4, 1917- jwuen toz HAQBEM May 13,1924,

E. HOPKINSQN PNEUMATIC TIRE CASING-FOR MOTOR VEHICLES Original FiledJan. 4, 1917 6 Sheets-Sheet 2 wiN May 13, 19246 3,493,674

- E. HOPKINSON PNEUMATIC TIRE CASING FOR MOTOR V-EHTCLES Original FiledJan. 4, 1917 6 s t -s t 4 May 13, 1924.

. E. HOPKINSON PNEUMATIC TIRE CASING FOR MOTOR VEHICLE I5 Original Filed1917 6 Sheets-Sheet 5 an own 01,

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E. HOPKINSON PNEUMATIC TIRE CASING FOR MOTOR VEHICLES Original FiledJan. 4, 1917 6 Sheets-Sheet 6 Patented May 13, W24.

cares STATE,

ERNEST HO'PKINSON,

OF NEW YORK, N. Y.

PNEUMATIC TIRE CASING FOR MOTOR VEHICLES.

Original application filed January 4, 1917, Serial No. 140,508. PatentNo. 1,374,505. Divided and this application filed March 7, 1921.

T 0 all whom it may concern I Be it known that I, ERNEST HorKiNson, acitizen of the United States, residing in New York city, county of NewYork. and State of New York, have invented certain new and usefulPneumatic Tire Casings for Motor Vehicles, of which the following is afull, clear, and exact description.

The present invention relates to vehicle tires made of rubber andfibrous materials, and particularly to pneumatic tires of heavy strongframes having thick wall structures such as are necessary for motordriven vehicles. An object of the invention is to provide a new tire ofvery much improved quality and capable of manufacture less pensivelythan prior. casings.

The present application is a division of my pending application formethod of making motor vehicle tires, Serial No. 140,508, filed January4, 1917, which has since become Patent No. 1,374,505, granted AprilTires for motor-driven vehicles are now usually madeby forming orshaping strips of fabric, whether woven or consisting of parallelthreads mainly held together by rubber, on a heavy metal core ofsubstantially the shape of the cavity of the tire casing when inflatedon the wheel with which it is-designed to be used. After all theelements going to make up the tire casing have been assembled on such acore, it is placed while still on the metal core within outer moldmembers and subjected to great pressure by means of a hydraulic press ina closed chamber which is heated to the desired temperature for thenecessary period of time to effect vulcanization. There are variationsof this method in practice, but in every case. the fabric or threads orcords which constitute the carcass of the tire are formed on a metalcore of the shape of the tire cavity. In all cases where the fabric isapplied in circumferential strips there is no tension on the threadsduring vulcanization and the path of any given thread over the core isnot the shortest path from edge to edge but merely the variablehaphazard re- Selial N0. 450,183.

sult of shaping a flat strip of fabric from the crown or periphery ofthe core to the edges.

By my invention strain resisting elements or threads may be formed intoa multi-ply carcass shaped like a pulley band in such manner andarrangement as to obtain, precisely, any desired condition of tension inthe threads in the finished tire. While the threads of any one layer orply are under substantiallythe same tension, it is possible to have thethreads of one layer relative to the threads of another layer underequal or unequal tension. And further, by varying the width of thelaminations or strips of the strain resisting threads, the tension onall of them in the finished tire may be governed to conform to thedictates of the best practice. This same result may be obtained withoutvarying the width of the strips by changing the angles of the threads inall the plies.

In actual practice I preferably lay sepa-,

rate plies of thread fabric successively on each other to form a pulleyband, the angles of the threads of succeeding plies having beenpredetermined with respect to a given tire cavity so that it is possibleto form the pulley band into the form and size of tire casing withrespect to which the calculations of the angle variations have been madeand so that, at such size and shape of tire casing all the threads ofall the plies are under similar conditions of tension in the finishedcasing before it is inflated for use, and the tire casing when inflatedfor use will not substantially increase its dimensions.

I will first explain the principle on which the carcass of the tire isbuilt.

In Fig. 1 the dotted lines indicate a strip of fabric of parallelthreads. In this strip the line A B is one of the threads and coincideswith the hypothenuse of the right angle triangle A B C of which B O isthe base and A C the vertical side. If a strip of fabric like thatillustrated in Fig. 1 be laid around a drum illustrated diagrammaticallyin plan in Fig. 2 (actual construction explained hereafter), each of thethreads, for instance A B, will be in contact with the face of the drum,the vertical side A C becoming the circumferential distance A C whilethe base B C, being the width of the strip, will be maintained. Now inactual practice this strip of fabric and the number of superposed pliesnecessary to give the desired strength, are caused to assume the shapeof a pneumatic tire casing by lifting the central portion throughout theentire circumference and moving the edges toward each other. Butconsidering this action as applied only to one strip and referring onlyto one thread A B in order to clearly explain the principle involved,the points A and B will be moved to A B and the thread A B will take(approximately) the path of the dotted line a in Fig. 2. Now assume thetire cavity to be represented by the core shown in cross-section in Fig.3, I have found that in a 36 x 4:} inch tire the thread A B with anangle of fifty degrees to the base B C and considered as the hypothenuseof a right-angle triangle, must have a base meas uring thirteen andthree 'quarter (13%) inches in order that it may lie in contact with thesurface of the core while maintaining the circumferential distance A Cwhich is equal to the vertical side A C. The thread A B is shown indotted lines in Fig. 5 in-contact with the surface of the core. But thesurface of the same core from edge to edge, on a right angle section isonly ten and one-half (10. inches, so that if the base B C were a threadit would be three and one-quarter (3%) inches longer than necessary toextend from edge to edge over the core at right angles. If therefore, weshould lay a strip of fabric with the threads lying at an angle of fiftydegrees (50) to the base like that of Fig. 1 on a drum, and then buildup on this ply any imaginary pliable material to the proper thicknessand then we should lay a strip of fabric whose threads lie at rightangles to the edges of the strip like B C and then move the edges ofsuch a composite band towards each other to the points A B indicated inFig. 2, the thread AB would lie in contact with the core without tensionand the thread B C would likewise lie over the increased surface fromedge to edge Without tension. The supposed construction is illustratedin Fig. 4 in flat cross-section and in tire shape in Fig. 3, the fillingmaterial being designated by the letter E. Therefore, it follows thatafter we have laid the first ply in position we may lay a second ply ofthreads directly over the first ply around the drum at such an angleapproaching the right angle of the thread B C so as to exactlycompensate for the increase in the circular distance resulting from. theapmeagre plication of the first ply when the plies are moved into tireshape, and so that the threads of the second ply will lie over the firstply in the same tension condition as the threads of the first ply lieover the core while maintaining the same lateral width or basemeasurement B G. I have indicated such a thread by the line F G in Fig.1, this second ply thread being laid at an angle of forty-nine andone-half (49:?)

ric of the carcass before turning the edges over the retaining wires.

Fig. 9 is a plan View showing the edges of the fabric of the carcassturned over the retaining wires and the various elements of the treadconstruction applied.

Fig. 10 is a cross-section of the completed casing in pulley-band form.

Fig. 11 is a View, partly in side elevation and partly in section,illustrating the form ing device, while Figs. 12 and 13 are detailedviews of the retaining rings shc wn in Fig. 11.

Fig. 14 is a cross-section of a mold enclosing a tire and tube, whileFig. 15 is an enlarged detailed cross-section of one edge of the flatpulley band.

Fig. 16 is a diagrammatic view of a sheet of fabric illustrating thecutting of the fabric strips.

Referring'now to the actual construction of a tire embodying myinvention, I take a sheet of fabric consisting of parallel threads whichmay be held together simply by unvulcanized rubber or by a weak weftthread woven across the main warp threads at intervals of approximatelyhalf an inch, which is an ordinary method of holding the warp threadsparallel. Assuming such a sheet of fabric properly rubberized either byskim-coating or solutioning or by any other desired method. I cut thesheet into strips at the desired angles.

I will now describe the building of a 36x4 inch tire casing, the carcassof which is made up of six plies of thread fabric of .04 inch thickness,attached to or supported by a sheet of rubber of .007 inch thickness.

The first step is to cut the various plies of the desired width and atthe predetermined angle. L have fcund by actual measurement Ill] meaevethe fourth ply, forty-eight and one-half seven and one-half (47-.1-)degrees.

(48%) degrees; in the fifth ply forty-eight (48) degrees; and in thesixth ply forty- These figures are not absolutely correct butpractically correct and such .as I have used in actual practice. I willhereafter describe how I have arrived at these various angles.

To obtain strips with the proper angles the full width of the fabric isout along lines which are the complements of these desired angles; thatis, the first strip will be cut at an angle of forty (40) degrees to theedges of the fabric, the second ply strips will be cut at an angle offorty and one-half (404) degrees, the third at an angle of forty-one(41) degrees, the fourth at an angle of forty-one and one-half (414)degrees, the fifth at an angle of forty-two (42) degrees, and the sixthat an angle of fortytwo and one-half (42. degrees. The various stripsare illustrated in Fig. 16, which shows in dotted lines a piece offabric with the various strips outlined thereon. Of course in practiceall the fifty degree (50) strips will be cut successively and then allthe forty-nine and one-half (494) degree strips, then the forty-nine(49) degree strips, and so on, so that there will be no waste in cuttingstrips at different angles from the same piece of fabric. It will alsobe understood that the width of the strips will vary, as the edges ofthe fabric when laid around the drum will bestepped, either outwardly orinwardly, as hereafter explained.

Assuming we have a supply of the necessary strips of fabric, I takestrip number 1, illustrated in Fig. 16, and lay it around a collapsibledrum 13.which is suitably mounted ona pedestal 14. The ends of the stripare abutted together so as to form a complete band without lap as thelast thread at the end of the strip joins up to the first thread of thestrip by the turning of the drum. In Figs. 6 and 7 I have illustrated aform of collapsible drum suitable for thepurpose. It is unnecessary hereto describe the drum construction in detail. In practice the drum ishalf way collapsed before the application of the first ply. I next applystrip number 2 with the threads running in the opposite direction,joining the ends of the then apply the layers numbers 3 and 4 and the-ninterpose another strip of separating material 16 at the edge portionsand finally lay on the plies 5 and 6. The next step is to place't-hecircumferential wires 17 in position. To do this, the drum is completelycollapsed in order that the wires may be readily placed overthesuperposed plies into position one from each side of the drum. Oncethe wires are located in position, the drum is expanded so as to tightlypress the layers of fabric against the wires 17. Then the edge portionsof the various layers are folded over the wires from each side, twoplies being folded over at a time. This operation of folding over twoplies at a time is permitted and made easy by the interposition of theseparating strips 15 and 16. After the fifth and sixth plies have beenfolded over, the separating strip 16 1S thrown to one side and plies 3and 4 are folded over. Then the separating strip 15 is removed and thefirst two plies placed in position on the drum are also folded over thewire. The next operation is to apply a layer of rubber 7 (illustrated inFig. 9).

This rubber strip 7 does not extend from edge to edge of the casing butonly across the tread portion and is in fact what is known as thecushion stock in the regular construction of tire. Over this rubberlayer 7 I place two plies of thread fabric 8 and 9, the threads of theseplies being spaced apart and serving as the breaker strips. I next applya layer of rubber 10 similar to the layer 7 and then apply two morebreaker layers of fabric 11 and 12 and finally apply the tread rubber12". The threads of the breaker layers 8, 9, 11 and 12 are laid atangles of 44, 439 42, and

41- to the axis respectively. Instead of the breaker strips herereferred to, the ordinary square Woven bias-cut fabric may be used andthe width of these breaker strips may be varied as desired. The casingis now complete inpulley band form as illustrated in Fig. 10.

The next operation is to cause the pulley band to assume approximatelythe U-shape of the finished casing. This I do by lifting the center andsimultaneously forcing in the edges, which operation I preferablyperform in the manner and by means of apparatus illustrated in Figs. 11,12 and 13, although any other desired manner and means may be availedof.

Referring to Fig. 11, the framework of the machine consists of twouprights 18 and a cross-piece 19. Extending from the crossiece to thebase are two threaded rods 20, each of which has secured to it a bevelgear 21, meshing with a bevel gear 22 on shafts 23, each of which shaftscarries a bevel gear 24, driven by bevel gear 25 which is connected byany suitable means to a source of power. Centrally located between theuprights is a cylinder 26 on which rests a removable ring 27, which inturn supports a removable ring 28. The ring 27 is provided with acentral circumferential channel 29 in which is located an inflating tube30 having a valve 31. Two forcing rings 32 are provided, each of whichis carried on arms 33 having a threaded engagement with the rods 20.

The operation of causing the carcass to be shaped to the form of thetire casing from the flat pulley band form is as follows: The rings 32are in their positions furthest apart from each other (the position ofthe upper ring indicated in dotted lines in Fig. 11) and the ring 27 isresting on the cylinder 26 while the ring 28 is entirely removed. Thisleaves enough space between the top of the ring 27 and the lower edge ofthe ring 32 to permit of the easy insertion of the pulley band casing.It will be understood that the ring 27 carries the tube 30 ready forinflation at the proper time. The lower flange with its retaining ringare then placed in position. There are two flange and retaining rings,one to co-act each edge of the casing. Each of these devices comprisesan endless flange ring 34 having a shelf or inwardly extending portion35 and a slotted outwardly extending portion 36. Each of the retainingrings consists of a broken ring of spring metal 36- having projections37 beveled on their lower faces and extending into the slots in theoutwardly extending portion 36 of the flange 34.

The pulley band casing is now placed in position, as indicated in Fig.11. Then the ring 28 is placed in position resting on ring 27 andfinally the upper flange and retaining ring are placed in position.Power is now applied to gear 25 causing the rods 20 to turn, carryingthe forcing rings 32 towards each other. This brings the rings 32 intothe positions shown in full lines in Fig. 11, the inward extension 35 ofeach of the flanges 34 being forced somewhat under the edges of thepulley band casing so that there is a clearance between the innersurface of the pulley band casing and the outer surface of the rings.The further movement of the forcing rings 32 is accomplishedsimultaneously with the admission of air under pressure to theinflatable tube 30 which lifts the central portion of the pulley band asthe forcing rings 32 move the edges of the easing towards each other toa circumferential line on each side of the channel 29 coinneeaera aidingwith the slots 39; and when projections 37 of the retaining rings cometo position over these slots they snap into engagement with the slots tolock the flanges in position. Sufficient air pressure is admitted to theinflatable tube to cause the casing to assume tire shape as shown indotted lines in Fig. 11. The flanges 34 being locked to the ring 27 bythe engagement of the projections 37 in the slots 39, the gear 25 is nowreversed to move apart the forcing rings 32; then the ring 28 is liftedoff the ring 27, which is also lifted off, carrying with it the casingand inflated tube locked in'position by the flanges 34 and the retainingrings whose projections 37 are engaging the slots 39.

Afterthe air pressure has had time to act on the casing to more or lessset it in tire shape the casing is taken off the ring 27 to bevulcanized. For this purpose I preferably use a special mold consistingof an annular base 40 for the tire (Fig. 14), a bull ring 41, outer moldmembers 42, and straps 43, these straps 43 occurring at intervalsthroughout both the inner and outer circumferences of the mold andserving to keep the mold members 42 together against the internalpressure. In Fig. 15 I have shown in section a modification of the edgeconstruction of the casing, the first ply in this instance being thenarrowest. Of course various modifications of this sort may be made ifdesired.

To return for a moment to the pulley band casing it should be noted thatfor the size of tire (36 x 44;), the building of which I havespecifically described. if my first ply consists of parallel threads atan angle of to the axis, the base B C (Fig. 1) must be 13% inches inorder to give sufficient length to the threads (A B of Fig. 1 forinstance) to pass over the desired core or rather casing cavityunstretched and withl the circumferential distance A C (Figs. 2 and 5).But I cut the first ply fifteen and one-half (15%) inches wide. andsucceeding plies fifteen (15) inches, fourteen and one-half (14%")inches, fourteen (14") inches. thirteen and one-half (13-3 inches, andthirteen (13") inches, and lay the plies around the drum with theircenters coinciding, and then place the side wires (17) on top of thelast ply eleven and one-quarter (114") inches apart (Figs. 8, 9, and10). After the portions of the plies extending beyond the side wires 17have been folded over. a portion of all the plies eleven and one-quarter(114") inches wide is held by the side wires 17 to form the carcassduring the forming process above described. Now if the threads are tolie over the desired casing cavity without tension, the lateral distancebetween wires must equal the base B C which is thirteen and sesamethree-quarter (13%) inches, therefore, when I place the wires eleven andonequarter (11%") inches apart the inflating process of formation whencompleted in the vulcanizing operation must stretch the threadsconsiderably and this is one of the objects of the invention. However,while I have placed the side wires 11); inches apart, the distance overthe core or rather the casing cavity at right angles is only ten andone-half (10%") inches, so, on the one hand the threads are stretchedlongitudinally while the width of the pulley band or the distancebetween retaining wires is diminished during the formation of the tirefrom the pulley band form. And this actually occurs in practice. Thedistance be tween the wires of the pulley band 'in the tiresspecifically considered is 11% inches while in the finished form of thesame tire measured over the cavity of the casing it is only 10%. This ofcourse comes about because the threads of each ply, are compelled tomove into a (generally speaking) spiral path in which they lie on thetread portion at an angle greater than the original angle of the flatstrip. That is to say, in the forming operation the portions of thethreads adjacent the bead members and along the sides tend to preservetheir angular relation to the axis of the pulley band more than theintermediate or central portions of the threads over the tread of thecasing. This is diagrammatically and roughly approximated in theillustration of Fig. 2. As a matter of fact the threads of the first plywhich are at an angle of 50 on the flat, take on an angle ot59 on thetread portion of the finished tire. Again: The tire casing in its pulleyband form has a diameter of twenty-seven (27) inches while the diameterat the periphery of the outer ply of the carcass in the finished tire(leaving the tread rubber out of consideration) isthirty-five (35)inches; or a difference of twenty-five (25) inches in circumference. Onemight expect therefore that the threads on the tread portion of thefinished tire would be spaced farther apart than in the pulley bandform. But this is not so. In the forming process the threads on thetread portion have all passed through a parallelogram movement toproduce the increase in angle just spoken of and they are in. factcloser together on the tread ofthe finished tire than in the pulley bandform.

Going back now to the placing of the tire in the vulcanizing mold itwill be apparent from the explanation immediately foregoing that theformation by inflation before described has not cause the casing toassume its final dimensions, so that when it is placed in the moldconsisting of the mold members 42and rings 40 and 41'it does not fillthe mold cavity. It is not necessary to detail the manual processesof'taking the casing off the ring 27 and placing it in the mold, exceptto say that an air-bag or inner tube (either green, semi-vulcanized orfully vulcanized) is placed in the casing and fluid pressure introducedinto the tube or air bag. In actual practice I use a semi-cured tube 44having substantially the dimensions shown in dotted lines in Fig. 1 1which approximates the cavity of the casing after it has been taken offthe ring 27 and the bullring 41 inserted and before the introduction offluid pressure in the tube 44:. In using a tube to inflate the casingduring vulcanization, I accomplish two distinct improvements in that Isave the expense of air-bags which ordinarily last only five or six"vulcanizations and at the same time save the expense of a portion of thevulcanization of the inner tube and obtain a much improved tube in thatit is exactly shaped to the tire cavity. In detail I take a tube whichhas been semi-cured only sufficiently long to partially set the jointswhile leaving the outer surface slightly sticky. I then applyone ofvarious substances to the outer surface of the tube and the innersurface of the casing to keep the tube separate from the casing duringvulcanization. For this purpose I have successfully used glycerine,talc,graphite, starch, powdered mica, and the paint powder known as aluminumbronze. I prefer the last mentioned because it leaves the outer surfaceof the tube and the inner surface of the casing with a beautiful silveryappearance and will serve as a lubricant between the casing -and tubewhen in use. After the coating process the tire and easing areassembledand placed in the mold, I then introduce fluid preferably at a pressureof one hundred eighty (180) pounds to the square inch and place the moldin a heater for a predetermined period, depending on the character ofthe rubber compounds used. I prefer to use CO as the fluid pressuremedium, although other mediums may be used. -During the vulcanizingprocess the internal pressure of course increases, due to thevuloanizing heat which is commonly about 280 I. The heat also acts tosoften the rubber and hence the internal pressure finds less resistanceto its forming action of the casing during the vulcanizing process thanwhen the casing is cold, so that the easing is caused to be pressedfirmly against the inner surface of the mold members and the ineaeraportions are made the subject of the claims, leaving other portions tobe claimed in other up lications. I

ome of the advantages of the invention are as follows: lit permits ofthe formation of the casing of an automobile tire in pulley band formnotwithstanding its necessarily thick heavy construction. This in itselfis of great importance for various reasons. The tire may be built muchmore quickly and cheaply than by any other process. The apparatus ismuch simpler, cheaper, and lighter than is necessary in an otherprocess. The usual heavy core an necessity for its manipulation areentirely done away with. The threads of the different plies may besuccessively laid at such angles as to exactly compensate for increasein size resulting from the application of previous plies so that theinflating process may act to shape the pulley band into tire shape. itmakes it possible to so locate the side rings as to produce in thevulcanized tire a carcass in which the threads are actually undertension independent of any stretch resulting from inflation in use. Allthe threads lie along substantially their shortest paths ;trom edge toedge. This results in a minimum of internal strains and stresses underthe flexing action in use, so that the plies do not separate from eachother. it permits of laying the threads at any desired angle. That isthe first ply may be laid at and so on. succeeding plies being laid atcorresponding angles. This is very important, because the shape of thefinished tire under inflation in use largely depends on the angles atwhich the threads are laid, the general proposition being that thegreater the angle of the threads to the axis of the tire the flatter thetire will be on the tread and the less the outward pull on the sidewires. And in a tire in which the natural effect of inflation results ina flattened tread and correspondingly greater rounded shape to the sidewalls, a greater wearing surface is obtained on the tread, and theflexing point in the side wall is not localized but distributedthroughout a greater length of side wall which in turn comprises a muchgreater length o; threads. To illustrate, the specific tire the buildingof which I have described, when molded in a mold designed for anordinary tire, showed a decrease of one inch in circumference on theperiphery and an increase in lateral cross-section at the widest pointof one-half inch after inflation as compared with dimensions takenbefore inflation. This effect is enhanced in a tire made up of plies offabric in which the threads lie at reater angles to the axis than in thetire re erred to. In a tire made according to my invention,- the carcassflexes as a unit. Again, there is absolutely no waste in the buildingoperation. The plies are cut to exact size and require no trimming.Another feature that may be referred to is the fact that anyconfiguration of the tread rubber may be obtainedin a single vulcanizingoperation as against the necessity for separate vulcanization of treadand can ease and an additional vulcanizing operation to unite the twowhich obtains in the ordinary process of manufacture where an anti-skidtread is desired. incidentally, the cost of vulcanizing the inner tubeis lessened and a better tube obtained. In a tire made by the ordinaryprocess of smoothing a flat strip over a core the shape of the tirecavity, the threads of outwardly succeeding plies are longer than thethreads of preceding plies and the threads of all the plies aredistorted out of their shortestpaths, whereas in my tire the threads ofsucceeding plies are shorter than in preceding plies and all the threadsof all the plies lie in substantially their shortest paths by an amountexactly determined by the angle at which they lie when flat which willallow all the threads to take their natural and substantially shortestpaths roni edge to edge and when in tire shape to be all under the samecondition of stretch. It will be seen too that as all the plies are laidon the drum at the diameter of the edges of the casing, there is a greatsaving in the amount of fabric used, as each ply is shorter and becauseof the unity of action between all the plies, fewer plies are needed.Again the threads of fabric are closer together at the tread portionwhere relative rigidity and resistance are required and are spacedfurther apart and the intervening spaces filled with rubber at the sideportions where flexibility is desirable.

lit the threads in the fabric strips are laid at a still greater angle,that is to say. commencing in the first ply with threads at an angle of60 to the axis. 1 have found that the side wires need not beinextensible, but in lieu of inextensible wires 21 simple winding ofcord may be used to define the edges and form a folding line for theprojecting edges of the fabric strips going to make up the carcass. Ithas been shown that the width between the edges of the tire casing whenin the pulley band form. is controlled by the angle of the threads inthe various plies, so that with a pulley band in which the threads ofthe first ply are at an angle of 60, the width must be still greaterthan that indicated. The forming action diminishes this lateral,distance of the pulley band to the desired lateral distance necessaryfor the particular tire cavity in mind, and therefore the threads movecloser together. This imposes the necessity that the threads shall bespaced sufficiently 21 art in the pulley band form to permit this actionto take aaeaaaa place. In such a tire the edge of the casing isextensible when uninflated so that it may be pried over the side flangeof a one-piece rim. The result of inflation to riding pressure is tocause the threads to so act on the edges of the tire casing as to bindthem to the surface of the rim and cause a hugging action and there isno outward pull on the edges of the casing.

I may say that it is important. to determine the angles of the threadsin succeeding plies with substantial accuracy, because, mathematicallyconsidered, there is only one angle variation between plies which willpermit of obtaining exact compensation in any given ply for the increasein circumference in underlying plies resulting from shaping plies of thesame width from pulley hand form to the form of a torus. This may bedetermined mathematically, but the calculations are very complex. Toenable others to practice the invention, the angles may be determined inthe following manner: Having determined the size of tire desired, thenumber of plies of fabric, thickness of cushion stock and thickness oftread stock, as also the desired inflated cavity, I first make an arc ofa core of the cross sectional shape and size of such desired cavity;then let us say we decide that the threads of our first ply shall be atan angle of 50 flat, we first find what length'of a thread at that anglewill be necessary to pass from edge to edge of the core. A simpleapparatus is desirable for this empirical method of deter mining theangles. Take a portion of a wide drum of the diameter of the edges ofthe core, lay the thread on the drum, preserving the 50 angle when fiat,which simply means that the circumferential distance between the ends ofthe thread shall be the same as the altitude A C (Fig; 1) for a givenlength of thread. Secure each end of the thread to clamping devices,both of which are capable of being moved to and away from the center ofthe face of the drum and one of which is capable of being movedcircumferentially. Then. place the core along the center of the drum andmanipulate the thread and thread-holding devices by moving them towardand away from the core (and. one of them circumferentially) until acircumferential distance between the two ends of the thread is obtained,which coincides with the altitude of A C of Fig. 1 for a length ofthread (hypothenuse A B of Fig. 1) which it has been found will exactlylie over the core from edge to edge and which when laid on a flatsurface will lie at the desired angle of 50. The base B C will then bemeasured. A second core is now substituted for the first core,

' the second core being a fac-simile of the first core augmented in sizeby an amount equal to the first ply. Now we go through the same processto find the angle of the secondply, always maintaining the lateraldistance or base measurement B C, because, clearly, the problem requiresit, as the retaining Wires in the actual construction define thesamelateral distance for all plies. This operation is repeated for eachply.

Of course various modifications may be made without departing from thespirit of my invention. For instance, I have described the entire casingas made fiat. If desired, only the carcass need be made fiat and thedesired tread construction applied after the carcass has been shapedfrom pulley band form to tire form. Further, the particular form ofbreaker construction here described may be used or the ordinary biascut,open-mesh woven fabric may be employed and applied to the carcass inpulley band form or after it has been formed to tire shape.

Throughout the specification I have emphasized the feature ofsuccessively varying the angles of the threads in the several plies of.rubberized fabric, because that feature in my opinion, is essential toobtaining the best results; but it will be apparent that the method ofconstruction of the tire casing here described may be utilized in athread fabric tire in which the threads of the several plies are of thesame angle, as also in a tire casing made of woven fabric. While I havespecifically described and illustrated a straight side tire casinghaving an inextensible wire located in each edge, the casing may be madewith an extensible clincher bead, or may be .of the quick detachabletype, or may be made with a straight side but without any wire in theedge, so that it will be extensible. In the case last mentioned, thethreads will be of the construction re ferred to in the specification,in which the threads are laid at a comparatively great angle (say 65) tothe axis of the tire, so that the elfec't of the internal pressure willlno tend to lift the tire from the side flanges of the rim. I

When in the claims I speak of a tire casing made of a plurality ofstrips of rubberized fabric formed into an unvulcanized multi-ply pulleyband, I mean by the words plurality and multi-ply to refer to aconstruction composed of two or more plies.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A. tire casing for motor vehicles comprising a carcass composed of aplurality of plies of rubberized fabric, the circumferential distancebetween the ends of any thread in the ply nearest the air chamber beinggreater than in the threads of the successive superimposed plies, thethreads being stretched in the vulcanized casing when uninflated.

ascents 2. A tire casing for motor vehicles comprising a carcasscomposed of a plurality of plies of rubberized fabric, the threads ofwhich are closer together at the tread portion than along the sidewalls.

3. A tire casing for motor vehicles comprising a carcass composed of aplurality of plies t rubberized cord fabric, the threads of which arecloser together at the tread portion than at the sides and are stretchedin the vulcanized casing when uninfiated.

l. A tire casing for motor vehicles comprising a carcass composed of aplurality of plies of rubberized cord fabric, the threads of one plybeing discontinuous from the threads of another ply and stretched in thevulcanized casing when uninfiated.

5. A tire casing for motor vehicles comprising a carcass made up of aplurality of layers of rubberized fabric, the threads or one ply beingdiscontinuous from the threads of another ply, each or the threads ofthe respective plies lying along the shortest path from a point on oneedge of the casing to a point on the opposite edge of the casingcircumterentially spaced apart therefrom.

6. A tire casing for motor vehicles comprising a carcass composed of aplurality of layers of rubberized fabric, the threads of the ply nearestthe tire cavity bridging a greater circumferential distance while thethreads in each succeeding ply are successively shorter and bridgelesser circumferential distances, all the threads of all the plies ofthe carcass being under tension when the casing is uninfiated.

T. A tire casing for motor vehicles con prising a carcass composed of aplurality of plies of rubberized fabric, the threads or each ply beingdiscontinuous from the threads of other plies, the ends of the threadsor" the ply nearest the tire cavity extending from one edge of thecasing to-the opposite edge being circumferentially spaced apart I whilethe threads of succeeding plies extend from edge to edge and havingtheir ends successively nearer to each other, all the threads of all theplies being under tension.

8. A tire casing for motor vehicles having a carcass formed ofsuperposed plies of strain resisting elements which in any one ply arearranged in substantial parallelism only and which in adjacent plies areinclined oppositely, in development the strain resisting elements ofeach ply at the tread being more nearly parallel to its edges thanStlitlibIQSlStlIlg elements each of the plies,

being closer together at the tread than at the outwardly bulged sides ofthe casing.

10. A pneumatic tire casing for motor ve hicles having a plurality ofseparate and discontinuous layers of strain-resisting elements, all ofwhich elements in any one layer are substantially parallel but extend atan opposite inclination to those of other layers, the strain-resistingelements in cross-section of the casing); being spaced apart more widelyin the outer than in the i ner layers, and a tread firmly anchored to 2carcass by vulcanized rubber of maximum thickness peripherally betweenthe elements in the outermost layers.

11. A pneumatic tire casing for motor yehicles having a plurality ofseparate layers of discontinuous parallel cords from a sheet thereof atan acute angle to the length of the sheet and rubberized, tne cords ineach layer being arranged at the abovementioned acute angle immediatelyadjacent the margins of the casing.

12. A pneumatic tire casing for motor vehicles consisting of vulcanizedrubber and a plurality of separate layers of discontinuous parallelcords, the cords of some of the layers being, arranged at an oppositeinclination to those of other layers, and all the cords throughout theirextent from one margin of the casing to the other occupying natural andself-assumed positions in cooperative relation forming a uniformhomogeneous carcass.

Signed at New York, county and State of New York, this th day of March,1921.

ERNEST HOPKINSQN.

